package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExcutor implements Executor {
    @Override
    public <T> int update(Configuration configuration, MappedStatement mappedStatement, Object... objects) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        //注册连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3、获取预处理对象prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSql());
        //4、设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parameterClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(objects[0]);
            preparedStatement.setObject(i + 1, o);

        }
        //5、执行sql
        return preparedStatement.executeUpdate();
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... objects) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InstantiationException, IntrospectionException, InvocationTargetException {
        //注册连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3、获取预处理对象prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSql());
        //4、设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parameterClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(objects[0]);
            preparedStatement.setObject(i + 1, o);

        }
        //5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        //6、封装返回参数集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objectArrayList = new ArrayList<>();
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名称
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或内省，根据数据库和实体的对应关系，完成封装。
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objectArrayList.add(o);
        }
        return (List<E>) objectArrayList;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            return Class.forName(parameterType);
        }
        return null;
    }

    /**
     * 完成对#{}使用？进行代替，并把#{}中的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler paramterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", paramterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = paramterMappingTokenHandler.getParameterMappings();
        return new BoundSql(parseSql, parameterMappings);
    }
}
